ITV bosses have apologised after broadcasting footage of stand-in judges watching a performance during the Britain's Got Talent first semi-final.

The talent show was accused of being 'fake' by eagle-eyed viewers, who noticed a woman with bright blonde hair sitting in Alesha Dixon's seat during a performance by singing duo J-Unity on Monday night.

The footage was broadcast during the recap at the end of the performance show as hosts Anthony McPartlin and Declan Donnelly summarised the night's acts and read out the phone voting numbers.

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Who are they? Four people who were obviously not the judges watching J-Unity during the recaps on Monday's Britain's Got Talent

Spot the difference: (L-R) Simon Cowell, Amanda Holden, Alesha Dixon and David Walliams watching J-Unity perform during the live show

As J-Unity - comprising of twins Jerome and Jamal - performed Olly Murs' song Troublemaker, the camera panned back to show four people - who were obviously not Simon Cowell, Amanda Holden, David Walliams and Alesha - sitting at the judges; panel.